Industrial paint application robots are used for painting objects such as, e.g., car bodies. In order to have an automated paint shop with a high degree of flexibility, such industrial paint application robots need to be prepared to apply paint material with a larger number of different paint colors, for example 20 or 30 colors. Typically, color changers are provided at the robot in order to provide paint material with different paint colors directly at the robot. A color changer typically comprises a larger number of input channels for supplying the respective paint material and which lead to a common output channel. Each input channel is provided with a paint valve, so that each of the input channels can be selectively connected with the output channel, which typically leads to a painting device located at a tip of the robot. As the paint color required to be applied during a production process is normally subject to relatively frequent changes during the production process, color changers need to be capable of performing relatively frequent color changes during the production process. It is desirable to reduce the waste of paint material during such color changes.
It is of immense importance for the quality of the painted objects that the applied paint material is not contaminated with a paint material of a color different than the color desired for the painted object. Therefore, a cleaning process is typically required, at the output channel and at the painting device, after each color change. Such cleaning process typically involves applying a cleaning solvent from a dedicated supply line through an output channel leading to the painting device. Furthermore, it is typically necessary to ensure that only one paint valve of the input channels is opened at a particular point in time so as to prevent a mixing of paint materials with different colors in the output channel. An object which has been painted with contaminated paint material typically constitutes waste, and in the worst case, cannot be reused.
Typically, an interlock of the paint valves is based on control logic of, for example, the robot controller, and which controls not only movement of the robot but also the switching operations of the paint valves. A mechanical interlocking mechanism is typically not provided for the paint valves. Paint valves normally comprise, e.g., a spring mechanism, which acts to close the paint valve in a steady state without the need of any further action.